My move to supralapsarianism is pretty recent. I remember discussing and debating with my Calvinist friends back in the dorm rooms during my undergrad years. One thing was this issue of infra/supralapsarianism and I would debate it. Ironically, in debating against supralapsarianism for so long I started to see the harmony with it. To be clear, I don’t think any amount of biblical exegesis can derive the logical order of the fall and election. These types of positions are supported by exegesis and arrived via theological reflection.
I can see the tension between libertarian free will and supra. This is how I understand it: Logically prior to the creation of the universe (natural knowledge and middle knowledge, moments 1 and 2), God chose to create to glorify himself and to share the intratrinitarian love between the godhead. His chosen method was to redeem a people to himself. What are the necessary conditions for this redemption (remember, necessary conditions are the consequent in a conditional statement, so: If X obtains, then redemption [where X is the sufficient condition])? There must be evil/sin and consequently death. So since God’s decision to redeem a people to himself, there had to be sin. Is God the direct cause of sin? No. I think that’s metaphysically absurd. What must be required? Free agents.